Actors have learned how to saddle up since the advent of Hollywood. But rarely does a job call for riding a horse while furiously swinging a mallet — and charging at Zendaya buried in the dirt up to her neck.

As Alamo Brown, the towering strip club tycoon and self-proclaimed “king of pussy,” Adewale Akinnuoye-Agbaje had six weeks to train for a 30-second scene, a wince-inducing cliffhanger in which he nearly knocks Rue’s head clean off her body.

“That was some of the best acting I’ve done in the show,” says the Nigerian British actor, chuckling, “because you couldn’t tell I was truly petrified of falling off the horse.”

Akinnuoye-Agbaje is the big bad in Season 3 of “Euphoria,” his screen time nearly matching Zendaya’s. We meet him in the first episode, sandwiched between four women in a hot tub, wearing nothing but a snakeskin Speedo, a gold chain and a cowboy hat. Alamo rescues Rue from her indentured servitude to one drug lord and brings her into his equally dangerous orbit of outlawry.

His impulsiveness and violence drive the tension in the season, which finds the central group of friends grown up and scattered across Los Angeles, their bad decisions unprotected by the guardrails of suburbia.

“They’re no longer in high school and are going out into the Western frontier of life, trying to make their way — some legitimately and some illegitimately,” Akinnuoye-Agbaje says. “Alamo represents a rude awakening for these young adults, and the consequences for their choices.”

Akinnuoye-Agbaje broke out as the ruthless prison-gang leader Simon Adebisi in “Oz” before taking on warlord-turned-priest Mr. Eko in “Lost.” Over his three-decade career in Hollywood, the 58-year-old actor has embodied kingpins, monsters and, in “Game of Thrones,” a slave trader. He calls “Euphoria’s” murderous sex cowboy “one of the most intense roles and processes I’ve had in my career.”

For nine months, Akinnuoye-Agbaje maintained Alamo’s accent, trading his affable London lilt for a menacing Southern growl. “Not being able to be fully present as myself with friends, family and just life was a sacrifice that I was happy to make to create a great character,” he says.

Even after “Euphoria” wrapped, Akinnuoye-Agbaje struggled to shed Alamo Brown. “It takes me about a month to get out of the accent and get back to myself,” which involves exaggerating his natural voice to recalibrate. Touching his cheeks, he says, “You see me clean-shaven — this is part of the process of taking him off of me.”

“It might even take me two weeks to shave, because it feels weird to do it straight away,” he says, laughing. “I almost have to give Alamo a respectable exit.”

Embodying a kingpin whose empire is built on exploitation and murder was challenging for Akinnuoye-Agbaje, who is a practicing Nichiren Buddhist. For two hours a day before arriving on set, Akinnuoye-Agbaje chanted, “Namu-myōhō- renge-kyō,” a mantra that helps him find stillness. “It’s really important that I have a spiritual anchor, so I don’t get caught up in some of the dark vibes,” he says. “You have to know your boundaries — who you are and what you feel you can delve into without getting snatched.”

As “Euphoria” approaches its climax, Rue is secretly working with the DEA as an informant while her life remains in Alamo’s hands. With one episode left, Akinnuoye-Agbaje is anxious for viewers to see how their game of cat and mouse (or shall we say cat and rat?) resolves.

“It’s quite a voracious fan base. Occasionally I’ve looked at my comments, but I try to stay away from it because it’s the audience’s show, and it preceded me,” he says. “But what I have seen is how people have embraced the character of Alamo. Even though he does present an ominous threat to our beloved Rue, they still love to hate him.”